There is a method for testing by the use of an image device whether a part is properly mounted on, for example, a printed wiring board. For example, it is known that the method includes steps for emitting light onto a part to be tested, for reading with a charge coupled device (CCD) camera, and performing image processing.
A method for performing automatic test by the use of an image of terminals 6 of a press-fit connector 2 that is press-fit exists as a method for checking, by appearances, whether a press-fit connector as an example of a mounted part is correctly pressed into a printed wiring board, as illustrated in FIG. 1A. In this case, an image of the respective tips of the terminals 6 of the press-fit connector 2 pressed into a printed wiring board 14 is captured with a CCD camera by emitting light onto the printed wiring board 14 from the lower surface side thereof to check the mounting status, as illustrated in FIG. 1B and FIG. 1C.
Japanese Laid-open Patent Publication No. 06-084078 (e.g. Abstract, paragraph 0018, and FIG. 1) discuss a test device for a fire detector as a test device in which a retroreflective substrate is used. The test device for a fire detector includes a retroreflective substrate attached to a place corresponding to the viewing angle of a light receiving element. In the test device for a fire detector, a fire detector and the monitoring area may be readily checked by the use of the retroreflective substrate. A test tool is observed from a position at a predetermined height, and it is checked, by the appearance of the retroreflective substrate attached to the test tool, whether a position to be checked is within the monitoring area of the fire detector.
Moreover, Japanese Laid-open Patent Publication No. 2006-324057 (e.g. Abstract, FIG. 4) discuss a method for press-fitting a press-fit connector in which, even when variations in the thickness of a printed wiring board occur, a constant press-fit height of a press-fit connector into terminal holes is maintained. One of the side of press-fit terminals and the side of a printed wiring board or a bus bar in which terminal holes are provided to be set as a fixed side, and the other side is set as a movable side. The movable side is moved up or down toward the fixed side. A contact position between the respective tips of the press-fit terminals and the printed wiring board or the bus bar or a position at a predetermined distance from the contact position is set as a reference position, and a sensor is provided at the reference position. When the sensor detects that the movable side has reached the reference position, the movable side is stopped after being moved a predetermined movement distance from the detection position so as to maintain a constant press-fit height of the press-fit terminals into the terminal holes.
In the printed wiring board 14, due to improvement of the speed of transmission signals, when the terminals 6 of the press-fit connector 2, which is press-fit, protrude from the lower surface side of the printed wiring board 14, as illustrated in FIG. 1A, since the protruding terminals 6 are close to each other, as illustrated in FIG. 1B, noise is picked up, and thus a disadvantage arises in that product characteristics may not be satisfied. FIG. 1C illustrates the magnified appearance of each of the protruding terminals 6, as viewed from the back side of the printed wiring board 14. Thus, an arrangement in which, even in a state in which the press-fit connector 2 is correctly press-fit, the tip of each of the terminals 6 does not protrude from the lower surface of the printed wiring board 14, as illustrated in FIG. 2A, may be adopted.
In a method for emitting light onto a terminal portion as a method for testing the mounting status of a part, when the terminals 6 are set to protrude from the printed wiring board 14, as illustrated in FIG. 3A, the presence or absence of the terminal portion may be checked, as illustrated in FIG. 3B. In contrast, when the terminal portion does not protrude from the printed wiring board 14, as illustrated in FIG. 2A, even in the case of a nondefective product, the emitted light may be weakened because the tip of each terminal is located within a corresponding through hole 16, as illustrated in FIG. 2B. Thus, it is difficult to determine the mounting status on the basis of an obtained image.
Moreover, in the case of a defective product in a state such as buckling because one of the terminals 6 is not correctly pressed into a corresponding one of the through holes 16, as illustrated in FIG. 4A, the light emitted onto the terminal 6 is further weakened. Thus, it is extremely difficult to determine the mounting status, as illustrated in FIG. 4B. Accordingly, in view of, for example, variations in reflected light, it is difficult to set a threshold value for determining a nondefective product and a defective product. As a result, a problem occurs in that the mounting status may not be determined.
When image capturing is attempted with the intensity of illumination being increased, so to avoid the aforementioned problems, a pass/fail test may not be performed because of the amount of diffused reflection from a land increases and a captured image is whitened. Moreover, when a threshold value for the pass/fail test is decreased, the probability that a defective product is erroneously determined as being a nondefective product increases, and thus a problem occurs in the quality.
Moreover, there is mounting test for parts in which the mounting status of parts 208 mounted on the printed wiring board 14 is monitored by obtaining a surface image of the parts 208 by the use of image information obtainer 22 (e.g., a camera), as illustrated in FIG. 5. However, when large parts 202 and 206 are mounted around a small part 204, as illustrated in FIG. 6, light is cut off by the large parts 202 and 206, so that sufficient reflected light to check the mounting status may not be obtained. Thus, mounting test in which the image information obtainer 22 is used has a problem. On the other hand, recently, the packaging density of parts mounted on a printed wiring board has been increased, and thus it has become difficult to arrange, in advance, large parts so that the parts are apart from each other. In such a case, test of the mounting status needs to be performed by visual observation. Thus, a problem occurs in that individually performing visual test decreases the efficiency of test and the overall efficiency of product manufacturing.